Photography Without a Telescope

If the comet can be seen by the naked eye it can be photographed using an ordinary 35 mm camera, with a standard 50 mm lens. The film used should however have a speed of 400 ASA or higher. The camera should be fixed to a tripod, set at infinity and aimed at the comet. Set the exposure dial to "B" position. Use a cable release for starting exposures. Try exposures ranging from 15 seconds to 1 minute. A hood in front of the lens will help in restricting the background light, that can fog the film during long exposures. For longer exposures it will be necessary to track the comet. Instructions to build a tracking device are given below.

How a simple and easily moved equatorial mounting for a camera can be made by the amateur is shown in the figure. Attach plate 2 to base plate using a triangular piece of wood so that the two form an angle equal to the local geographical latitude. Attached to plate 2 by means of a hinge is plate 4 carrying on its upper edge a ball tripod-head for securing the camera. The axis of the ‘hinge’ must point towards the celestial pole when photographing - check this with a compass or according to the Pole Star. Firmly attached to plate 2 is a nut in which is fitted a bolt with rounded end touching plate 4. Distance X between the axis of the bolt and axis of the hinge should be such that one turn of the bolt, the height of thread W, corresponds to an angular rotation of plate 4 (together with the camera) of I minute of time or 0.25 degree of arc. X = W : (1.00274 x tan 0.25ø) = W x 228.5. For example, if W = I mm, then X = 228.5 mm. In practice all that needs to be done then during exposure is to turn arm 3 concurrently with the movement of the second hand of a watch.

A simple tracker for Astrophotography